1. Field of the Invention
This invention relates to a lid assembly for pressure containers and the creation of an opening and closing mechanism therefor. A shutter device constructed according to this invention is most suitable for use in a pressure container having an internal treating chamber adapted to be controlled alternately to have a pressurized state and a depressurized state.
2. Description of the Related Art
As is known in the art, since lids for pressure containers, such as autoclaves for medical use and retorts for food processing, require strength and fluid tightness, they are constructed of relatively thick, heavy-weight members. An opening and closing mechanism connected to such a lid tends to be a necessarily large-sized rugged structure in order to attain reliability and safety in operation. According to a known lid and a known lid opening and closing mechanism, there is provided a lid body which is sized to suit the opening and the lid body is supported for opening and closing on a support shaft in the lateral surface, so that when the opening is closed, the front ends of a plurality of clamping rods on the lid body engage the peripheral edge of the opening to lock the entire lid body.
In the field of storage and transport techniques, as shown in Japanese Utility Model Publication No. 14406 to 1978, there is proposed a lid device (of the lift type) comprising a dome-shaped lid body adapted to be lifted from the position in front of the opening in a container to an upper retracted position by a link mechanism including a hydraulic cylinder and a bell crank. Further, as in the case of Japanese Utility Model Publication No. 21 of 1981, there are some known ones (of the slide type) wherein an angularly shaped lid body is adapted to be moved vertically or horizontally between guide rails on opposite sides of the container through a chain and sprocket device (for example, Japanese Utility Model Publication No. 45807 of 1974, and Japanese Patent Publication No. 45949 of 1982).
Although these known lid devices are substantially satisfactory in strength, they require a wide space for moving the lid body during the opening and closing operation. Besides these, there are many other known ones which, in the opened state, require a wide storage space for the lid body outside the container. This is a limiting factor in installing a pressure container in a limited space in a factory or facilities, obstructing wide use of large-sized pressure containers.
On the other hand, concerning ideas relating to storage of a lid or shield plate for shielding the opening, there are proposed a shutter mechanism for houses as described in Japanese Utility Model Publication No. 41985 of 1980 and a carrier shutter for refrigerator cars as shown in Japanese Utility Model Publication No. 30728 of 1980. They comprise a number of shutter panels connected in the longitudinal direction (direction of movement), such shutter panels being adapted to be bent at junctions between adjacent panels during the opening and closing operation. Therefore, when such shutter panels are used, all panels can be moved along the outer housing surrounding the shield space until they are stored compactly in a desired place.
This type of shutter is useful in that the storage space therefor can be minimized, but has received no proper attention as to retention of fluid tightness, particularly pressure resistance in a state where a pressure above atmospheric pressure is present.
Generally, in the case where a pressure-resistant type lid structure is applied to a pressure container such as an autoclave for medical use, proper measures must be taken as to the fact that at the same time as the entire lid body together with the pressure container is pressurized, it is heated as well. In reality, in treatment by an autoclave, sterilization treatment is performed usually at a pressure of 1.5-2.0 kg/cm.sup.2 and a temperature of about 130.degree. C., or drying treatment is performed at a reduced pressure of about -760 mmHg; therefore, it is required that the lid and the lid opening and closing mechanism be capable of resisting both pressurized and depressurized states and have sufficient heat resistance.